Lineage reprogramming, whereby cells of adult organs are converted from one specialized cell type into another, has emerged in recent years as a promising approach to regenerate cells lost due to disease or injury. This regenerative approach could prove valuable for the treatment of Type 1 diabetes where insulin secreting -cells are destroyed by autoimmune attacks. The long-term goal of this proposal is to devise strategies to reprogram adult cells of endodermal organs into pancreatic ?-cells for cell replacement therapies. In a recent study, our research groups showed that pancreatic exocrine cells can be reprogrammed into insulin secreting ?-cells in adult animals by a combination of three transcription factors. We propose to expand on this study and build a set of new tools to investigate the mechanisms of reprogramming and study the reprogramming of several related endodermal cell types, including pancreatic exocrine cells, liver cells and intestine cells, into -cells. In Specific Aim I, we will develop a new generation of viral vectors to dissect the molecular and epigenetic mechanisms of in vivo reprogramming of exocrine cells into ?-cells. In Specific Aim II, we will develop inducible mouse genetic models to investigate the in vivo reprogramming of adult endodermal cells to ?-cells. In Specific Aim III, we will use chemical and genetic screens to reprogram hepatocytes to ?-cells ex vivo. Together, these studies are expected to yield important insights into the mechanism of ?-cell reprogramming and help define additional cell types and reprogramming methodologies to regenerate ?-cells in the adult. Such tools and knowledge will form the foundation for developing novel cell replacement therapies for Type 1 diabetes.